Space-time coding and multiple-input, multipleoutput wireless system promise to deliver higher data rates with higher reliability than traditional systems, with no increase on transmit power or bandwidth. In this expository paper, we present multiple-antenna systems and their ability to increase the number of dimensions that may be transmitted per channel use. We present two space-time codes, one that is oriented towards maximizing the data rate (V-BLAST) and the other towards increasing reliability (Alamouti). We present a third option, a hybrid code, that has the advantages of both types of coding. This code belongs to the general class of linear dispersion codes, and it has a particular structure that allows the design of a hardware receiver with very low complexity.